07/18/2026
When now the smoke seems to be a problem for more days, Dr van Wessum put together some scientifically based information to explain what to do and what NOT to do. Dr van Wessum is a ACVSMR board certified specialist in Equine Sports Medicine and Rehabilitation, which gives him great insight in how to deal with sport related problems, and he is board credentialed by the Dutch AVMA in Equine Medicine.
The first remark is to realize how your barn is. Most barns will not have an air filtration system, so the air in the barn is the same as the air outside. With required good ventilation (especially with higher temperatures - and ammonia vapour from the stalls can really damage the lining of the lung, much more damage than inhaling particles will do) there needs to be a high air turnover, so outside air is inside air. That means there is no advantage to keeping horses in 24-hours. Being outside in early morning, when temperatures are relatively low and do not trigger a higher respiration frequency, being outside has one GREAT advantage: the horse’s head is down while grazing, and mucus and debris can easily be moved from deeper airways to the trachea and out. This will not happen that way when locked in the barn. The mucociliary clearing (little whip hairs that move mucus from deeper airways to the trachea) is the best defense mechanism the horse has against small, inhaled particles, and we take that partly away by keeping them inside. When they are inside, feed hay from the ground for that reason!
Second point is that when horses are in the barn only, some small parts of the lung will no longer be used in breathing, and smoke particles can get lodged in into those lung parts, giving a breeding ground for infection later (it can cause pneumonia!). When the horse is walking for 10-15 minutes at east, those lung parts stay open, ventilated and with adequate blood flow, which again is a big part in the defense mechanism for the horse’s airways. Take them out for a walk in the morning or do some walking exercises in the arena to keep your horse’s lungs healthier!
Research has shown that ANY particles in the lungs of the horse in the healthy horse are removed within 24 to maximum 48 hours. There is NO need to wait 3 to 4 weeks after the smoke has cleared before starting to work again. It is even detrimental, because normal function of the lungs is limited when at stall rest (while most barns are not “clean”, often many dust and even fungus particles load the airways more than when they are outside or at work).
The mistake that is made here is that the longer period of 3 to 4 weeks is when the horse has been exposed to fire with smoke. Hot air from a fire will damage lungs much more than inhaling just some particles, and that is where the confusion stems from.
Only when your horse has a pre-existing long problem (allergies, COPD) then it may take much longer to clear the airways.
When starting to work again you should pay attention to your horse, when it is breathing faster or shallower, or has some mild exudate in the nose or does cough a bit, then take it easy and reduce workload. Being outside in the morning is still encouraged!
We hope to have explained some of the misunderstandings and misinformation that is out there by a specialist in the field with large scientific credentials to keep us all doing the best for our horses and let’s hope we can return to a more normal situation soon.
